For safety reasons, I cannot recommend that you attempt to glue these belts back together. The seams on Shopsmith Belts have been "taped" seams for many years...fused together under a special process (that you will be unable to duplicate) at the abrasive manufacturer.
As you probably realize, it is imperative that these seams remain flexible while being EXTREMELY strong. If you tried to use epoxy glue for its strength, it would not be sufficiently flexible. If you tried to use rubber cement for its flexibility, it would not be sufficiently strong.
Since your safety should be far more important to you than saving money, our best recommendation is that you tear (or cut) your damaged belts into strips or pads and use them for sanding lathe turnings...or with your orbital or pad sander.
Any new replacement belts you may purchase should be hung vertically on your shop wall, over a protruding dowel and away from any moisture. Don't lay them flat, as they could crease.
Yep. Here are the sizes for the most common birds: